Fibrillated fibers and articles made therefrom

ABSTRACT

This invention relates to fibrillated fibers having particular physical characteristics, articles made therefrom as well as methods of producing the same. In particular the fibrillated fibers are defined by their Canadian Standard Freeness in combination with their Tensile Strength when formed into a sheet.

This is a divisional of co-pending application Ser. No. 07/408,587,filed Sep. 18, 1989 is now pending which, in turn, is a division of Ser.No. 06/918,246, filed Oct. 14, 1986 is now U.S. Pat. No. 4,929,502.

BACKGROUND OF THE INVENTION

The fibrillation of fibers, fibrillated fibers and their uses arewell-known to those skilled in the art. For example, U.S. Pat. No.2,810,646 to Wooding et al discloses a water laid web comprisingfiltered, heat-bonded, water-fibrillated, wet-spun filaments. Thefilaments are of a polymer selected from the group consisting ofpolymerized acrylonitrile and a copolymerized mixture of acrylonitrileand up to 15%, by weight, of at least one other monomer copolymerizabletherewith. U.S. Pat. No. 4,495,030 to Giglia discloses the use of afibrillated fiber to provide cohesiveness and support to a wet-laidsheet containing active carbon and submicron glass fibers. U.S. Pat. No.4,565,727, also to Giglia, discloses the use of a fibrillated fiber toprovide cohesiveness and support to a wet-laid sheet containing activecarbon in the form of carbon fibers and carbon particles.

Various nonwoven structures using a fibrillated acrylic fiber weredisclosed in Giglia et al; Novel Nonwoven Activated Carbon Fiber Paperspresented to a meeting of the American Chemical Society in April of1984.

Recently, there has been much interest in the possible use of nonwovenfabric technology to produce paper and felt like structures containingactivated carbon for use in chemical protective clothing and filteringapplications including both gas and liquid filtering. The aforementionedGiglia paper described several nonwoven adsorptive felt like structureshaving loadings of activated carbon fibers or powders. In that paper itwas disclosed that a fibrillated acrylic fiber, produced according tothe process set forth therein, was useful in permitting high loadings offiller materials, such as activated carbon fibers and powders in thenonwoven fabric while maintaining good wet strength and chemicalresistance.

While many binding agents have been available in the past, fibrillatedfibers are becoming of interest as they provide fine diameter fibrils asopposed to those of heavier spun fibers. Generally, spun fibers areproduced in sizes of ten microns or greater while it has been theexperience that sizes of less than a micron (cross section) are requiredto entrap and bind fine particles in nonwoven and other compositestructures. Need exists now, however, for binders which provide suchentrapment properties which also provide reinforcement and strength tocomposite constructions. While the fibrillated fibers of the prior arthave provided adequate and improved characteristics, recognized needsfor further improvement in this field are apparent and a welcomecontribution to the art would be a fibrillated fiber having highlydesired physical characteristics of low Canadian Standard Freeness incombination with relatively high Tensile Strength. Heretofore, thelimits of these properties in the area of acrylic fibers has been suchthat fibrillated acrylic fibers have not been available with a CanadianStandard Freeness below about 200 and certainly not available incombination with a useful Tensile Strength such that the material couldbe processed on conventional nonwoven fabric lines. These and othershortcomings of the prior art have been remedied by the discovery of theinstant invention which will be described herein as follows.

SUMMARY OF THE INVENTION

The instant invention provides for a fibrillated fiber wherein saidfiber has a Canadian Standard Freeness (CSF) of less than 200 incombination with a Tensile Strength (TS), as will be defined herein, ofat least 5 pounds per inch and preferably a CSF of less than 100. Apreferred base fiber is of an acrylic nature with especially desirablefibers having acrylonitrile contents of at least 85% (based on weight ofacrylonitrile monomer content to total monomer content of theprepolymerization mixture). Particularly useful, fibers havepolyacrylonitrile content in excess of about 89% and more preferably,between 89 and 90% on the same basis as set forth above. The preferredcomonomers comprise methyl methacrylate which is preferably present atlevels of at least about 10% by weight as discussed above. Othercomonomers may be used without limitation provided that their inclusiondoes not materially detract from the ability of the fiber to befibrillated nor with the properties of the fibrillated fiber produced.Compatibility of such other monomers can easily be determined by oneskilled in the art by simple experimentation.

Extremely useful, fibrillated fibers and preferred for certain usesinclude fibers having a CSF of less than about 50 and/or a TS of atleast about 7 pounds per inch. Fibrillated fibers having CSF of lessthan about 25 are very desirable providing fabrications of extremeutility.

Included within the scope of the invention are nonwoven fabrics madewith the fibers summarized above and in particular, nonwoven fabricsfurther comprising a toxic vapor absorptive agent including, but notlimited to, activated carbon. In several uses said activated carbon cancomprise activated carbon fiber alone or in combination with a powderform present in said fabric at levels of up to about half the weight ofthe fabric, i.e. the total fabric including all components including theactivated carbon. Such fabrics can further comprise other fibersincluding, but not limited to, up to about two fifths, by weight, ofglass fibers. In cases where CSF values for the fiber are less than 100,amounts of activated carbon as described above may conveniently exceedhalf the weight of the fabric and in fact, can preferably exceed morethan three quarters the weight of the fabric and more desirably inexcess of about six sevenths and seven eighths, by weight, of thefabric.

Preferable fabrics independent of their composition are permeable to airand water vapor and provide improved components for such thingsincluding, but not limited to, breathing masks, garments and filtrationsystems.

Generally, sheets comprising about 5% to about 65%, by weight, of thefibrillated fiber can be used to bind powders, flakes and fibers ofvarious sources and descriptions. These materials include, but are in noway limited to, the activated carbon materials discusses above as wellas other synthetic (organic and inorganic, i.e. glass, silicon, boron orthe like) and natural fibers, powders, metallics, minerals and the like.These materials may be in sheets or may also be in the form of pelletsor, for example, pressed powders or any other form whereby the inclusionof the fiber provides improved integrity of structure.

DESCRIPTION OF FIGURES

FIG. 1 Graphic Representation of Data of Example 1 CSF

FIG. 2 Photomicrograph Example 1 Representative Fibers 15 min.

FIG. 3 Photomicrograph Example 1 Representative Fibers 25 min.

FIG. 4 Photomicrograph Example 1 Representative Fibers 35 min.

FIG. 5 Photomicrograph Example 1 Representative Fibers 45 min.

FIG. 6 Graphic Representations of Data of Example 2 CSF

FIG. 7 Graphic Representations of Data of Example 2 TS

FIG. 8 Photomicrograph Example 2 Representative Fibers 20 min.

FIG. 9 Photomicrograph Example 2 Representative Fibers 35 min.

FIG. 10 Photomicrograph Example 2 Representative Fibers 60 min.

FIG. 11 Photomicrograph Example 2 Representative Fibers 75 min.

FIG. 12 Photomicrograph Example 2 Representative Fibers 90 min.

FIG. 13 Graphic Representation of Data of Example 3 CSF

FIG. 14 Graphic Representation of Data of Example 3 TS

FIG. 15 Photomicrograph Example 3 Representative Fiber 50 min.

FIG. 16 Photomicrograph Example 2 Representative Fiber 70 min.

FIG. 17 Photomicrograph Example 2 Representative Fiber 90 min.

FIG. 18 Photomicrograph Example 2 Representative Fiber 110 min.

FIG. 19 Photomicrograph Example 2 Representative Fiber 130 min.

FIG. 20 Photomicrograph Example 2 Representative Fiber 150 min.

FIG. 21 Graphic Representation of Data of Example 4.

DETAILED DESCRIPTION OF THE INVENTION

The fibrillated fibers of the instant invention comprise in combinationa Canadian Standard Freeness of less than 200 in combination with aTensile Strength of at least 5 pounds per inch as will be hereinafterdefined.

Canadian Standard Freeness is measured as is described in a test setforth in an article entitled "Determination of Freeness" Standard C.l,Approved Method, October 1940, Revised May 1952, October 1962, September1967, June 1969 and April 1972, prepared by the Physical and ChemicalStandards Committee, Technical Section, Canadian Pulp & PaperAssociates.

Tensile Strength is measured according to Federal Standard 191A TM 5100as follows:

0.63 g (Dry Weight) of the fibrillated fiber is slurried in 200 ml ofwater. This slurry is then added to a 12.5 cm ID Buchner funnelcontaining a liner of No. 1 Whatman filter paper. Vacuum is used to forma test sheet on the filter paper layer. The test sheet is then separatedfrom the filter paper support and is dried to constant weight in an airoven at about 110° C. The resulting sheet is then cut into 1.0 inchstrips which are evaluated for tensile strength to break according toFederal Standard 191A TM 5100.

Preferably, fibrillated fibers having a CSF of below 100 and/or aTensile Strength of at least 7 pounds inch are particularly useful, andfibers having CSF values below about 50 and 25 are found to havedesirable and very desirable characteristics, respectively.

With regard to the fiber from which these fibrillated fibers are made,acrylic based fibers are preferable. In particular, those in which theacrylonitrile monomer contribution is at least 85%, by weight, of thefiber. By monomer contribution is meant the weight of the monomeremployed in the reaction mixture based on the total weight of allmonomer contained therein just prior to initiation of thepolymerization. Fibers with higher acrylonitrile monomer contributionare particularly preferred. Acrylic contents in excess of 89% aredesirable and particularly preferred are compositions where the contentis about 89 to 90 percent. While any compatible comonomer may be used,methyl methacrylate has been found to be particularly suitableespecially when its monomer contribution is at least 10%, by weight.Inclusion of other comonomers can be made with simple experimentationbased on the ancillary properties that they can provide provided thattheir inclusion does not materially detract from the ability to achievethe aforestated CSF and TS values critical to the instant invention.Without wishing to be bound by the theory, it is believed that fibersuseful in producing the fibrillated fibers of the instant invention arethose wherein the comonomer mix provides a fiber having lateral weaknessand longitudinal strength. When using acrylic fibers, the preferred formof the invention the fibrillated fiber precursor can be made byconventional wet-spinning methods. In the best mode contemplated at thetime of the filing of this application; wet-spun, gel, hot-stretched anduncollapsed acrylic fibers comprising about 90%, by weight, and 10%, byweight, acrylonitrile and methyl methacrylate monomer contributions areemployed. Specifically, contemplated comonomers that also may be usefulinclude other similar acrylates, such as, for example, ethyl acrylate.Similarly, homopolymers and copolymers of other fiber formingmonoethylenically unsaturated monomers, such as vinylacetate, vinylchloride, styrene, vinyl pyridine, acrylic esters, acrylamide and thelike are within the scope of materials contemplated herein. Examples ofstill other copolymerizable monomers which are contemplated includethose as described in U.S. Pat. No. 3,047,455.

The fibrillated fibers of the instant invention can be made using amodified commercial blender. In general, it has been found advantageousto use a modified Waring brand commercial blender wherein the assupplied blade has been modified to provide a break edge of about 0.25mm on the working edge. In operation a relatively dilute slurry orprecursor fiber in water is introduced into the blender device which isthen run for about at least one-half hour to about at least one hourdepending upon the molecular weight of the fiber being used. Withacrylic fiber having what is considered a high molecular weight, i.e.ca. 58,000, a process time as short as one-half hour was found to beadequate while with a material of what is considered a low molecularweight, i.e. ca. 49,000, a minimum of about an hour was required. Forthe invention the exact time of processing is not critical and will varywith the character and make-up of the precursor, i.e. molecular weightand monomer content and will be easily determined in view of thisdisclosure by simple experimentation. What has been found to be criticalwas control of the temperature of the slurry while it was beingprocessed. In prior art techniques, nd as will be demonstrated in theExamples to follow, no attention was paid to the heat of the slurrymixture. Irrespective of the normal starting temperatures, i.e. roomtemperature, the mechanical action of the processing resulted inimparting heat energy to the slurry and slurry temperatures in excess ofabout 50° C. were experienced. Fibers produced thusly had CSF levels ofabout five-hundred to seven-hundred, and values of less than that wereunable to be achieved prior to loss of useful Tensile Strength asdefined by these improved fibers. Importantly, it was discovered that byproviding means to maintain the temperature of the slurry in a lowerrange that the fibrillated fibers of the instant invention wereobtainable for the first time. In general, slurry temperatures, whenusing this technique maintained below about 30° C., produced fiberswithin the scope of the instant invention. It is contemplated within thescope of the invention that variation of the slurry temperature in andaround 20°-30° C. using the aforedescribed technique alone or incombination with variations of slurry solids content will enableinfinite variation of the critical parameters of CSF in combination withTS as may be required for the end use of the fibrillated fiber.

It is recognized that use of the commercial blender as described aboveis somewhat limited with regard to the amount of the fiber of theinvention which can be produced in any one batch. It has been found thatlarger amounts of the material can be produced using larger equipment.It is cautioned that many conventional cutting and beating devices havebeen attempted to date that do not produce fiber within the scope ofthat of the instant invention. It has been found that when a Daymaxbrand 10 gallon mixer was modified as per the modification on thesmaller Waring device (i.e. ˜0.25 mm break edge modification) 0.7%slurries of precursor maintained below 30° C. and processed for aboutfour hours produced fibrillated fiber within the scope of the invention.

Optionally, it has been found that use of a dispersant duringprocessing, such as, for example, Aerosol® OT-75, as available fromAmerican Cyanamid Company, Wayne, N.J., or any similar such materialfacilitates the processing. The exact blending parameters or theequipment employed are not limiting with regard to the scope of theinvention and it is contemplated that such may be varied and modifiedwith simple experimentation by one skilled in the art in view of thisdisclosure.

In accordance with the present invention, there is also provided animproved fabric comprising said fibrillated fiber alone or incombination with preferably a toxic absorbing agent or filtrationmaterial. In uses where said fabric will act as an element in afiltration system, it is preferable that said fabric be permeable to airand water vapor. Included within the scope of the filtration and toxicabsorbing agents are activated carbons either in fiber or powder form orin mixtures thereof either alone or in combination with other agents. Inone preferred mode the improved products of the present invention areprepared by wet-laying the activated carbon fibers, activated carbonparticles and fibrillated acrylic fibers from a water suspensionthereof. The suspension should contain from about 1-15%, by weight,based on the total weight of fibers and particles, preferably from about1-5%, by weight, of the fibrillated acrylic fibers, from about 6-75%, byweight, same basis, preferably from about 10-65%, by weight, of theactivated carbon fiber and from about 15-85%, by weight, same basis,preferably from about 20-70%, by weight, of the activated carbonparticles, the total weight of the three components being 100%.

The activated carbon particles, activated carbon fiber and fibrillatedacrylic fiber are wet-laid using the conventional paper-making processwell known in the art. Flocculating agents and surface active agents canbe incorporated into the water suspension in order to facilitate thepaper-making procedure as is also known in the art. The bulk of theacrylic fibrillated fibers should range from about 1 mm to about 10 mmin length.

The activated carbon fibers are also well known in the art as aremethods for their production. They can be used in lengths of from about0.3 to about 15.0 mm, preferably from about 0.5 to about 10.0 mm, andcan be prepared from such carbon fiber precursors as coal tar pitch,petroleum pitch, coal tar, petroleum derived thermal tar, ethylene tars,high-boiling coal tar distillates, ethylene tar distillates, gas oils orpolynuclear aromatics. Also useful as precursors are polymers, such asacrylonitrile homopolymers and copolymers, polyvinylalcohol,phenolic-aldehyde and natural and regenerated cellulose. Methods forpreparing activated carbon fibers useful herein are disclosed in U.S.Pat. No. 4,069,297 and 4,285,831, which patents are hereby incorporatedherein by reference.

The activated carbon powder or particles have a particle size rangingfrom about 0.1 to about 500 μm, preferably from about 1.0 to about 80 μmand are also prepared from any of the carbon precursors described above.

The wet-lay sheet making process (paper making) used herein for theproduction of the novel fabric material of the present invention resultsin a product having unique sorptive characteristics, a thickness of atleast about 0.005 inch, preferably at least 0.01 inch, a high sorptivecapacity to weight ratio and high porosity to fluid flow. Theequilibrium loading of absorptive carbon fiber is higher thanconventional activated carbon powder products. The products of thepresent invention are more porous than sheets containing only carbonparticles. The carbon fiber, which tends to lay parallel to the plane ofthe sheet, produces a longer fluid flow path through the sheet whichincreases the time available to adsorb impurities. The novel productshereof accept an unexpectedly high additional loading of active carbonpowder. The combination of active carbon fiber and active carbonparticles results in a higher performance versus cost ratio than sheetswhich contain only one of these active ingredients.

The surface of the novel fabric material of the present invention may beembossed during or after its production to improve sheet flexibilityand/or porosity. The novel nonwoven fabric material may be laminated toa woven, nonwoven, knitted etc. backing, such as matts, felts, papers,etc. produced from cotton, hemp, flax, ramie, jute, silk, wool, leather,flannel, flannellette, swansdown, poplin, cellulose ethers or esters,nylon, rayon, acetates, polythene, glass, rock wool, asbestos, in orderto strengthen the material.

Lamination of the novel products hereof to the above-mentioned backingmaterials may be achieved by the use of water vapor and air permeableadhesives, preferably those available in the form of foams, such asrubber or acrylic latexes, polyurethanes and the like. These adhesivesare self-adhering and upon curing foam and set into strong bonds.

The surface of the novel fabric material claimed herein may be renderedhydrophobic by coating with a porous silicone film or a polymer, such aspolytetrafluoroethylene. Additionally, a reactive coating capable ofdecomposing toxic agents, e.g. a coating of a sulfonated polymer tohydrolyze nerve gas, may be applied thereto so that the activated carbonparticles and fibers form a second line of defense.

The fabric material of the present invention has a wide variety of uses.It is useful for protective purposes and for filtration and separationof gases and liquids. The uses include the manufacture of the fabricmaterial into wearing apparel, e.g. military uniforms, blankets,sleeping bags, bedding, surgical dressings, wrappers and containers,covers, tarpaulins, tents, curtains, gas masks, paint spraying masks,air-conditioning duct filers, flue gas deodorizers and the like.

In general when fibers of the instant invention are employed having incombination CSF and TS values of less than two-hundred and five poundsper inch, it has been found that up to about one half of the resultingfibers weight can conveniently comprise activated carbon either in fiberor powder form. When the CSF value is reduced to below about 100, evenhigher loadings can be obtained. In increasing desirability theactivated carbon component of the fabric system can comprise more thanone half to three fourths of the fabric, by weight, and most desirablyto in excess of sixth seventh and even seven eighths of the total fabricweight. Additionally, major proportions of other fibers (i.e. glass upto about two fifths, by weight) and materials may be incorporated toprovide other desirable qualities to the fabric.

In addition to the critical parameters of the fibrillated fiber of theinstant invention, the fibers are further characterized by the followingexamples and related graphs and photomicrographs derived therefrom whichare provided for illustration only and are not to be construed aslimitations on the present invention except as set forth in the appendedclaims. All parts and percentages are as defined above unless otherwisespecified.

EXAMPLE 1 COMPARATIVE BASIS

A commercial Waring blender having a capacity of one gallon in theblending chamber was modified by providing about a 0.25 mm break edge onthe working edges of the blade. Next a slurry of an acrylic fiber, about0.56%, by weight, was made up in two liters of water to which was alsoadded 2 ml of a solution of 0.1 mg/100 ml of Aerosol® OT-75. Theparticular fiber, having a molecular weight of about 58,000, used wasthat sold by American Cyanamid Company under the designation of T-98 andhad an acrylonitrile content of 89.2% and a methyl methylacrylatecontent of 10.8%. The staple before processing had a length on averageof about three-eighths inch and a denier of about 5.4. The suspensionwas then charged to the blender and was then processed for a period offorty-five minutes. Aliquotes were removed from the process slurry at15, 25, 35, and 45 minutes and the temperature of the slurry was noted.The resulting fibrillated fiber from each aliquote was evaluated for CSFand TS as indicated in the body of the specification above. Inparticular, TS was made on a 100% sheet of 50.9 g/m² basis weight formedby adding about 0.63 grams (Dry) of the fibrillated fiber in 200 mlwater to a 12.5 cm lD Buchner funnel containing a liner of No. 1 Whatmanfilter paper under vacuum. Once the test sheet was separated from theliner and dried, it was cut into one inch strips and evaluated.

The resulting data is set forth in Table 1 and is graphically depictedin FIG. 1. As will be seen CSF values of the normalized plot were withinthe range of about five to seven hundred. The single point atthirty-five minutes is believed to be an anomaly and in any event had avalue in excess of 225. Additionally provided as FIGS. 2, 3, 4 and 5 arephotomicrographs of the resulting fibrillated fibers correspondingrespectively to the 15, 25, 35 and 45 minute aliquotes each magnified tothe same scale (note reference for scale comparison) showing the resultsof the fiber processing.

EXAMPLE 2

The procedure of Example 1 was repeated with the followingmodifications:

a) The Waring blender was fitted with a water cooling device such thatthe temperature of the slurry could be maintained between 24° C. and 30°C. during processing.

b) The blender was charged with a slurry containing 21 grams of fiber inthree liters of water (i.e. consistency 0.7%) to which was added 1 ml ofthe dispersant solution.

c) The blender was operated in the low speed mode for ninety minutes andaliquotes and temperature readings were taken after the 20th, 35th,60th, 75th and 90th minute of processing, which samples were evaluatedas before.

Raw data is shown in Table 1 and is graphically represented in FIGS. 6(CSF) and 7 (TS) with FIGS. 8 through 9 being the photomicrographs ofrepresentative fibrillated fibers from the 20th through 90th minutealiquotes, respectively. As will be seen from the graphicrepresentations of the data, the critical combinations of low CanadianStandard Freeness and high Tensile Strength were achieved withprocessing times greater than about one-half hour.

EXAMPLE 3

The procedure of Example 2 was repeated with the single exception (asidefrom processing times as shown) that a lower molecular variant(mw≃49,000) of the fiber was employed. Samples and temperatures weretaken after the 50th, 70th, 90th, 110th, 130th and 150th minutes ofprocessing. Raw data is presented in Table 1 and is graphicallyrepresented in FIGS. 13 (CSF) and 14 (TS) with FIGS. 15 through 20 beingthe photomicrographs of representative fibrillated fibers from the 50ththrough 150th minute aliquotes, respectively. As will be seen from thegraphic representations of the data, the critical combination of lowCanadian Standard Freeness and high Tensile Strength were achieved withprocessing times greater than about one hour.

EXAMPLE 4

The mixer blade of a Daymax 10 gallon mixer was modified as per themodification of the Waring blender in Example 1. The mixer tank was thencharged with about seven gallons of a slurry of the same fiber andconcentrations of Example 3. As will be seen from FIG. 21, a graphicalrepresentation of the raw data shown in Table 1 (running times of 2,21/2, 3, 31/2 and 4 hours) at the end of four hours CST dropped to 70and Tensile Strength was 11 lbs/inch, well within the critical limitsdefined herein. During the run, temperature was maintained vis-a-vis theapplication of about 50 lbs of ice per running hour.

                  TABLE 1                                                         ______________________________________                                        EXAMPLES 1-4                                                                  Example   Running  Temp       CSF  Tensile                                    No.       Time     °C. ml.  lbs/inch                                   ______________________________________                                        1          15 min  40         730  --                                                    25      45         650  --                                                    35      45         230  6.0                                                   45      52         650  --                                         2          20 min  --         290  2.1                                                   35      30          30  9.4                                                   60      26          29  9.7                                                   75      27          8   16.3                                                  90      --          38  12.9                                       3          50 min  <30        768  --                                                    70      <30        142  1.8                                                   90      <30         28  9.7                                                  110      <30         29  6.9                                                  130      <30         14  12.1                                                 150      <30         8   7.4                                        4          2 hrs   26         750  --                                                    21/2    --         650  --                                                    3       27         540  --                                                    31/2    22         200  --                                                    4       --          70  11.4                                       ______________________________________                                    

EXAMPLE 5

A mixture of 14% fibrillated acrylic fibers, 18% activated carbon fiberand 68% activated carbon powder in 18 l. of water if formed into a sheetusing a standard hand paper making machine. The sheet is dried underpressure at 70° C. to 120° C. The resultant fabric material is effectivefor the removal of toxic materials from vapor passed through it.

EXAMPLE 6

The procedure of Example 5 is again followed, except that 12%fibrillated acrylic fiber, 59% activated carbon fiber and 29% activecarbon powder are employed and the paper material is embossed afterforming but before drying. The resulting fabric material is effectivefor the removal of toxic materials from vapor passing through it.

EXAMPLE 7

The procedure of Example 6 is again followed, except that the fabricmaterial is not embossed. After drying the material is laminated to a65/35 polycotton fabric utilizing a commercially available acrylic foamadhesive. The resulting product is effective for the removal of toxicmaterials from vapor passing through it.

EXAMPLE 8

The procedure of Example 5 is again followed, except that 45%fibrillated acrylic fiber and 55% activated carbon powder are employed.No activated carbon fibers are present. The resulting fiber is effectiveat removing toxic materials from vapor passing through it.

EXAMPLE 9

The procedure of Example 6 is again followed, except that 6.3%fibrillated acrylic fiber and 93.7% activated carbon fiber are employed.No activated carbon particles are present. The resulting fabric materialis effective at removing toxic material from vapor passing through it.

EXAMPLE 10

The procedure of Example 5 is again followed, except that 19.4%fibrillated acrylic fiber, 80% activated carbon fiber and 0.6%polytetrafluoroethylene are employed. No activated carbon powder ispresent. The resulting material is effective against removal of toxicvaporous material.

EXAMPLE 11

The procedure of Example 6 is employed, except that 6.3% of fibrillatedacrylic fibers and 93.7% of activated carbon fibers are employed. Noactivated carbon powder is present. Two layers of the resultant fabricmaterial are laminated as in Example 7. The resulting product is usefulfor removing toxic elements: from air.

What is claimed is:
 1. A personal protection device incorporating anon-woven fabric material comprising a wet-laid sheet containing afibrillated monoethylenically unsaturated monomer based fiber having aCanadian Standard Freeness of less than 100 in combination with aTensile Strength of at least 5 pounds per inch.
 2. The device of claim 1wherein the fiber is an acrylic based fiber.
 3. The personal protectiondevice of claim 1 wherein said device is a breathing mask.